Update 2: Security firm Kaspersky Lab has recorded more than 45,000 attacks in 74 countries in the past 10 hours. Seventy-four countries around the globe have been affected, with the number of victims still growing, according to Kaspersky Lab. According to Avast, over 57,000 attacks have been detected worldwide, the company said, adding that it “quickly escalated into a massive spreading.”

According to Avast, the ransomware has also targeted Russia, Ukraine and Taiwan. The virus is apparently the upgraded version of the ransomware that first appeared in February. Believed to be affecting only Windows operated computers, it changes the affected file extension names to “.WNCRY.” It then drops ransom notes to a user in a text file, demanding $300 worth of bitcoins to be paid to unlock the infected files within a certain period of time.

While the victim’s wallpaper is being changed, affected users also see a countdown timer to remind them of the limited time they have to pay the ransom. If they fail to pay, their data will be deleted, cybercriminals warn. According to the New York Times, citing security experts, the ransomware exploits a “vulnerability that was discovered and developed by the National Security Agency (NSA).” The hacking tool was leaked by a group calling itself the Shadow Brokers, the report said, adding, that it has been distributing the stolen NSA hacking tools online since last year.

Predictably, Edward Snowden – who has been warning about just such an eventuality – chimed in on Twitter, saying “Whoa: @NSAGov decision to build attack tools targeting US software now threatens the lives of hospital patients.”

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Update 1: In a shocking revelation, The FT reports that hackers responsible for the wave of cyber attacks that struck organisations across the globe used tools stolen from the US National Security Agency.

A hacking tool known as “eternal blue”, developed by US spies has been weaponised by the hackers to super-charge an existing form of ransomware known as WannaCry, three senior cyber security analysts said. Their reading of events was confirmed by western security officials who are still scrambling to contain the spread of the attack. The NSA’s eternal blue exploit allows the malware to spread through file-sharing protocols set up across organisations, many of which span the globe.

As Sam Coates summed up…

NHS hack: So NSA had secret backdoor into Windows. Details leaked few weeks ago. Now backdoor being exploited by random criminals. Nightmare

Hospitals across the UK have been hit by what appears to be a major, nationwide cyber-attack, resulting in the loss of phonelines and computers, with many hospitals going “dark” and some diverting all but emergency patients elsewhere. At some hospitals patients are being told not to come to A&E with all non-urgent operations cancelled, the BBC reports.

The UK National Health Service said: “We’re aware that a number of trusts that have reported potential issues to the CareCERT team. We believe it to be ransomware.” It added that trusts and hospitals in London, Blackburn, Nottingham, Cumbria and Hertfordshire have been affected and are reporting IT failures, in some cases meaning there is no way of operating phones or computers.

At Lister Hospital in Stevenage, the telephone and computer system has been fully disabled in an attempt to fend off the attack.

NHS England says it is aware of the issue and is looking into it.

UK Prime Minister Theresa May confirms today’s massive cyber hit on NHS is part of wider international attack and there is no evidence patient data has been compromised.

Several experts monitoring the situation have linked the attacks to vulnerabilities released by a group known as The Shadow Brokers, which recently claimed to have dumped hacking tools stolen from the NSA.